In complex microscopic ecosystems, where hundreds or thousands of different species compete, many bacteria, fungi, and other organisms secrete toxic chemicals that disable or kill competing bacterial species. Alexander Fleming observed this process in 1928, when mold accidentally contaminated a Petri dish and killed a bacterial culture. His observation resulted in the discovery of penicillin, the first antibiotic drug.

Most new antibiotic drugs are derived from natural sources. These compounds disrupt critical functions in bacterial cells without harming human cells. Yet, bacteria eventually evolve to become resistant to these medications. Today, new strains of bacteria, including those that cause tuberculosis can resist most, and in some cases, all available antibiotics. Widespread use of antibiotics is accelerating the process.

“The evolution of drug resistance is an inevitable consequence of genetics and
natural selection when drugs are used against microbial pathogen....” – IOM 2004